Orthogonal Frequency Division Multiplexing (OFDM) is a method of digital signal modulation in which a single data stream is split across several separate narrowband channels at different frequencies to reduce interference and crosstalk. OFDM is a standard method of encoding digital data on multiple carrier frequencies for broadband wireless systems and is used for Wireless LAN, Fixed Broadband Wireless Access, and Digital Video and Audio Broadcasting.
Zero-IF (also known as homodyne, or synchrodyne) transceivers, where the local oscillator (LO) frequency is equal to the input-carrier frequency, are highly popular for WiFi devices because they enable low-cost OFDM terminals. This is in contrast to the standard superheterodyne receiver where the LO frequency is not equal to the input-carrier frequency so that superheterodyne is accomplished only after an initial conversion to an intermediate frequency. However, the zero-IF architecture introduces an IQ imbalance due mismatches between the parallel sections of the in-phase (I) and quadrature (Q) signal receiver and transmitter paths, which can have a significant impact on signal quality including a degradation in the Image Rejection Ratio (IMRR) from image interference.